Vehicle safety device

ABSTRACT

A vehicle safety device including an inflatable occupant restraint bag which is comprised at least in part of a woven stretch fabric which is permeable to fluid used to inflate the bag, the bag having a variable porosity which increases and decreases in relation to the fluid pressure within the bag.

United States Patent 1191 Bonn et al.

1451 Mar. 26, 1974 VEHICLE SAFETY DEVICE [75] Inventors: Clifford Bonn,Buffalo, N.Y.;

Kenneth R. A. Wilson, Redondo Beach, Calif.

[73] Assignee: Irvin Industries Inc., Greenwich,

Conn.

[22] Filed: Jan. 12, 1972 [21] Appl. No.: 217,308

Related US. Application Data [60] Division of Ser. No. 101,253, Dec 24,1970, and a continuation-in-part of Ser. No. 22,429, March 25, 1970,abandoned.

3,451,693 6/1969 Carey .1 280/150 AB 3,451,694 6/1969 Hass 1 280/150 AB3,222,016 12/1965 Boone 244/145 3,410,511 11/1968 Coppa 188/1 2,798,8207/1957 Nelson 117/44 x 2,066,639 1/1937 Masland 117/44 x 2,400,9905/1946 Hawley,.|r... 117/38 3,603,430 9/1971 Kendall 5/347 3,680,8868/1972 Mazelsky 2.80/150 AB OTHER PUBLICATIONS Automatic InflatableOccupant Restraint System, Kemmerer et al., l/l968, pp. 3 and 5.

Primary Examiner-David Schonberg Assistant Examiner-John P. SilverstrimAttorney, Agent, or FirmBrowne, Beveridge, De- Grandi & Kline [57]ABSTRACT A vehicle safety device including an inflatable occu pantrestraint bag which is comprised at least in part of a woven stretchfabric which is permeable to fluid used to inflate the bag, the baghaving a variable porosity which increases and decreases in relation tothe fluid pressure within the bag.

1 Claim, 4 Drawing Figures PAIENIEBmzs I974 8799574 sum 1 UF 2 ForcePS4.

Solid Fabric |0-- Woven Sfrefch Fabric FIG. 2

v 0 25 5O 3 Time Milliseconds Force RSJ.

Solid Fabric -----Woven Sfrei'ch Fabric zoo/30o Time MillisecondsVEHICLE SAFETY DEVICE This is a continuation-in-part of our applicationSer. No. 22,429, filed Mar. 25, 1970, now abandoned and a division ofour application Ser. No. 101,253, filed Dec. 24, 1970.

This invention relates to improvements in vehicle safety devices.

Inflatable occupant restraint bags previously considered have consistedof various designs, some of them being: (a) Those of materialimpermeable to the inflating fluid, relying upon various types ofblow-out patches which are designed to rupture upon increase of pressurewithin the bag as the occupant is impacted thereagainst; (b) others inwhich the bag has been provided with a plurality of openings and is of amaterial, such as polyethylene having a type of semi-permanent set orstretch after occupant impact thereagainst so that the openings thereofmay enlarge upon impact of an occupant thereagainst but will remain insuch enlarged condition for at least the time period in which the bagwould be useful in a given accident; and (c) others in which the bag hasa plurality of openings, some of which will be covered by impact of anoccupant thereagainst, causing increasing pressures in the bag as thesize of the occupant increases.

All of such previously considered inflatable occupant restraint bagshave proven unacceptable at least in part due to the fact that:

With respect to type (a) Since the bag is of material impermeable to thefluid, the pressures built up therein prior to rupture of the blow-outpatches have a tendency to cause the occupant to rebound from the bag,which may be injurious and, after rupture of the blowout patches, thereis not sufficient inflation to afford any protection in the event ofsecondary impact.

With respect to type (b) The openings, having once enlarged upon impact,are not reduced in relation to reduction of fluid pressure within thebag, thus being no better than blow-out patches in affording protectionin the event of secondary impact.

With respect to type (c) The instantaneous area of openings is notcontinuously variable according to fluid pressures in the bag, butremains either essentially constant or undergoes a sudden finiteexpansion. Therefore, the fluid flow through the bag is not undercontinuous control and the likelihood of rebound increases with the sizeof the occupant and the number of orifices he will cover on impact withthe bag.

Further, inflatable occupant restraint bags previously considered havecontemplated use of a plastic bag. Inasmuch as these bags will likely bestored in a fixed folded position for long periods of time, it isanticipated that the same will have a tendency to weaken along the foldlines thereof, which may cause them to rupture on sudden inflation andmay likewise acquire a set which inhibits fully operational inflationthereof.

The primary object of the present invention is the provision of avehicle safety device which includes impact bag means comprised at leastin part of a woven stretch fabric which is permeable to the fluid withwhich the bag means is inflated, the bag having a variable porositywhich increases and decreases in relation to the fluid pressure withinthe impact bag means. The present invention thus permits passage of theinflating fluid through the fabric, dependent upon the impact pressuresapplied externally to the bag means, and the build-up of internalpressure, thus reducing or eliminating the undesirable effects of highpeak forces and the secondary bounce or rebound associated withpreviously provided vehicle safety devices of this type.

A further object is the provision of an inflatable occupant restraintbag which affords protection in the case of secondary impact.

Other objects and advantages of the invention will become apparentduring the course of the following detailed description, taken inconnection with the accompanying drawings, and in which drawings:

FIG. 1 is a diagrammatic view of a vehicle safety device according tothe present invention.

FIGS. 2 and 3 are graphs depicting the typical force v. time curves ofpreviously provided vehicle safety devices of this type as compared withapplicants invention.

FIG. 4 is a graph illustrating a minimum, maximum, and suggestedpermeability flow profile of woven stretch fabric of the presentinvention.

ln the drawings, wherein for the purpose of illustration is shown apreferred embodiment of the invention, and wherein similar referencecharacters designate corresponding parts throughout the several views,the let ter A may designate an inflatable occupant restraint bagincluding fluid supply means B and impact bag means C.

Inflatable occupant restraint bag A may be suitably mounted on vehicleframe 10 by means of any appropriate mounting means. Since theinflatable occupant restraint bag will mainly be used in automobiles, itis obvious that the type of mounting will be dependent upon the locationin which the same is to be mounted, for instance, it may be mounted onthe dashboard in the case of the front-seat passenger side, possibly incombination with the steering wheel on the drivers side, and in variousother positions as is appropriate considering the size and type ofvehicle in which the same is to be mounted.

Fluid supply means B preferably includes a fluid source 12, and sensorvalve means 13 which is operative on crash impact to permit fluid flowfrom fluid source 12 and into impact bag means C. A diffuser 14 may beprovided for channeling fluid flow into impact bag means C.

Fluid source 12 may be of any acceptable design. For instance, in someinstances it has been suggested to provide a container filled withcompressedgases under extremely high pressures as a source for a fluidused to inflate an occupant restraint bag. Others have suggested the useof explosive devices and other means for instantaneous generation ofexpanding gases for inflation of the occupant restraint bag. Anysuitable type may be used in connection with our invention.

Sensor valve means 13 may likewise comprise any conventionallyacceptable sensing valve device. For example, there have been suggesteduses of both electrical and mechanical devices which are usually inertiaresponsive in that they will be actuable on crash impact, usually in therange of eight to twelve miles an hour in connection with automobiles,to provide for fluid flow from fluid source 12 to impact bag means Cvirtually instantaneously as the crash impact occurs.

Diffuser 14 may likewise by of any acceptable type, providing for readyrelease of fluid into impact bag means C and may also serve as a sourceof attachment thereto of impact bag means C to form a unitary inflatableoccupant restraint bag.

The characteristic of the fabric which is used to make the impact bagmeans and that enables a fluid to pass therethrough will be generallydesignated herein in terms of permeability. Permeability will beunderstood as referring to the volume of passing fluid per unit area pertime unit.

When reference is made to the characteristic of the entire bag meansthat enables a fluid to pass therethrough, the same will be generallydesignated in terms of porosity. Porosity may be understood as the ratioof openings and'orifices in the fabric in relation to the total area ofthe assembled bag.

Impact bag means C is preferably comprised at least in part of a wovenstretch fabric which is permeable to the fluid used to inflate the same.Inasmuch as it is believed that the safety device of this invention willmost likely include impact bag means C which is made entirely of a wovenstretch fabric which is permeable to fluid released from fluid source12, this is the form which has been shown in the drawing. Of course, itis to be understood that the entire impact bag means C does not have tobe composed of woven stretch fabric, but that such woven fabric could beused at only selected locations of the impact bag means, the remainderof the same being of a fabric impermeable to fluid from fluid source 12,the fluid permeable woven stretch fabric parts thereof acting in thenature of blow-out or rupturable parts of such bags, but wherein thepermeable woven fabric does not rupture, but permits regulated releaseof fluid from the bag, in relation to the fluid pressure within the bag.

A woven stretch fabric according to this disclosure is deemed to be onein which the warp, weft, or both include stretch yarns. The denier usedfor the warp is not necessarily the same as the denier of the weft, andthe specific denier used may be dependent upon the type and uses of thevehicle in which the same may be employed. The particular weave used mayalso be varied.

In brief, we seek to provide an inflatable occupant restraint bag ofwoven stretch fabric which has a suitable tensile strength and avariable porosity. Also, since we do not want a bag which may provideincreased porosity on impact and which increased porosity is at leastsemi-permanent, the woven stretch fabric of the present inventionpreferably has a virtually instantaneous recovery of at least 70 percentafter elongation under normal operating conditions.

We preferably employ a woven stretch fabric having a warp of hightenacity nylon and a weft of nylon clad spandex fiber.

A spandex fiber may be generically defined as a manufactured fiber inwhich the fiber forming substance is a long chain synthetic elastomercomprised of at least 85 percent of a segmented polyurethane. Lycra,manufactured by E. I. DuPont de Nemours & Company (INC.) is a type ofspandex fiber which we have found suitable.

A suitable woven stretch fabric is one having a warp of from 420-840denier high tenacity nylon and a weft of spandex fiber (such as Lycra)of 140-560 denier wrapped with ends of 210-420 denier high tenacitynylon. The spandex fiber is preferably woven under stretch of 150-300percent (well below the permanent set stretch point thereof). The warpis preferably comprised of 35-70 ends per inch, dependent on the denierselected, and the weft is preferably comprised of 2248 picks or fillsper inch, again dependent on the denier selected.

A specific example of a suitable woven stretch fabric is one which has awarp of 420 denier high tenacity nylon, 7O ends per inch, and a weft of560 denier spandex fiber under 300 percent stretch, wrapped with 2 endsof 210 denier high tenacity nylon having 45 picks per inch. This wovenstretch fabric will have a virtually instantaneous recovery of -95percent after elongation below permanent set.

It is, of course, to be understood that our invention is not limited tothe specifics of the woven stretch fabric above enumerated, others beingacceptable as long as they fall within the parameters of variablepermeability as herein set forth.

Referring to the graph of FIG. 2 and the designation of solid fabric,which is a substantially impermeable fabric presently used and in whichblow-out patches or some other type of rupturable device is used forrelease of fluid from the inflated occupant restraint bag. Taking thepoint of zero as the instant of impact, the bag is fully inflated toapproximately 2 pounds per square inch in about 25 milliseconds,pressures in the bag increasing to approximately 10 pounds per squareinch on occupant impact. This type of bag usually has a rebound peak, asdeflation through rupture of the bag occurs, indicated by the secondpeak of the graph, the solid fabric bag fully deflating in approximately80 to milliseconds.

In comparison, referring to FIG. 2 again, the woven stretch fabric isagain inflated in approximately 25 milliseconds, expanding under stressof impact of the occupant, permitting a greater or lesser flow of fluidthrough the woven stretch fabric, dependent upon the magnitude of thelocalized impact of the occupant thereagainst, and eliminating theundesirable effects associated with the high peak forces and secondarybounce of solid fabric restraint bags. The self regulating features ofsuch variable porosity contains peak forces within acceptable limits.

As shown, our improved woven stretch fabric inflatable occupantrestraint bag is likewise virtually instantly deflatable, after impact,in the order of from 80 to 100 milliseconds, but such deflation isrelatively constant rather than immediate and total as is the case withsolid fabric impact bags. As shown in FIG. 3, this is likely to beimportant in cases where a secondary crash may be involved, forinstance, in a vehicle which may impact against first one object andthen another. The solid fabric bag in which the blow-out patch orrupturable portion has been ruptured will provide less protectionagainst a secondary impact than a bag having a generally constant rateof deflation, through intact woven stretch fabric, providing a greaterdegree of retained pressure of fluid within the bag, so that the samemay still serve as an adequate restraint in the case of a secondaryimpact.

In FIG. 4 we have endeavored to further delineate a region ofsatisfactory fabric permeability. The curves shown are flow profilesunder impact conditions at a velocity of 30 miles per hour. As shown,the flow profile desirable is between a maximum of )t 114p and a minimumof )t 16.6p wherein A is the fabric permeability in terms of cubic feetof fluid flow per square foot per minute and p is the differentialpressure of fluid in the restraint bag in terms of pounds per squareinch gauge. A suggested permeability curve within such minimum andmaximum is )t 3.7p" at differential pressures of substantially 0.25 2.45pounds per square inch gauge and A SOP 40 at differential pressuresabove 2.5 pounds per square inch gauge within the range of differentialpressures to which such restraint bags will normally be subjected.

In some instances we have found that a fluid permeable plastic coatingmay be applied to a woven stretch fabric in order to more closelyregulate the variable permeability thereof. One such coating we havefound satisfactory is a polyurethane which has had salt mixed with it,the salt being leeched out to provide permeability. Application of suchplastic coating does not inhibit the basic characteristics of the wovenstretch fabric, for instance, the recovery after elongationcharacteristics thereof.

Various changes may be made in the shape, size and arrangement of partsherein shown and described without departing from the spirit of theinvention or the scope of the following claims.

We claim:

l. A vehicle safety device including impact bag means inflatable oncrash impact for protection of an occupant of a vehicle, a fluid source,and means providing for fluid flow from said fluid source to effectinflation of said impact bag means on crash impact, said impact bagmeans comprising at least in part a woven stretch fabric having aplurality of threads of stretch yarn extending in at least one directionin juxtaposition for elongation of the woven stretch fabric so thatinflating fluid permeability of the woven stretch fabric portion of saidimpact bag means is increased upon occupant impact against said impactbag means and upon increase of fluid pressure within said impact bagmeans by enlargement of the openings in said woven stretch fabricportion there of, said woven stretch fabric having substantiallyinstantaneous recovery of at least percent after elongation within therange of differential pressures to which such an impact bag means willnormally be subjected so that inflating fluid permeability thereof isdecreased upon decrease of fluid pressure within said impact bag meansand by dissipation of the forces of occupant impact against said impactbag means by decrease in the size of the openings in said woven stretchfabric portion thereof and having a permeability/pressure curve underimpact conditions at a velocity of 30 miles per hour and within therange of differential pressures to which such impact bag means will benormally subjected which substantially conform to the empirical formulaA 3.7p 20 at differential pressures of substantially 0.25 2.45 poundsper square inch gauge and substantially conforms to the formula A p 40at differential pressures above 2.5 pounds per square inch gauge,wherein A is fabric permeability in terms of cubic feet of fluid flowper square foot per minute and p is the differential pressure of fluidin the impact bag means in terms of pounds per square inch gauge, theopenings in said woven stretch fabric being continuously variable indirect relation to fluid pressures within said impact bag means.

1. A vehicle safety device including impact bag means inflatable oncrash impact for protection of an occupant of a vehicle, a fluid source,and means providing for fluid flow from said fluid source to effectinflation of said impact bag means on crash impact, said impact bagmeans comprising at least in part a woven stretch fabric having aplurality of threads of stretch yarn extending in at least one directionin juxtaposition for elongation of the woven stretch fabric so thatinflating fluid permeability of the woven stretch fabric portion of saidimpact bag means is increased upon occupant impact against said impactbag means and upon increase of fluid pressure within said impact bagmeans by enlargement of the openings in said woven stretch fabricportion there of, said woven stretch fabric having substantiallyinstantaneous recovery of at least 70 percent after elongation withinthe range of differential pressures to which such an impact bag meanswill normally be subjected so that inflating fluid permeability thereofis decreased upon decrease of fluid pressure within said impact bagmeans and by dissipation of the forces of occupant impact against saidimpact bag means by decrease in the size of the openings in said wovenstretch fabric portion thereof and having a permeability/pressure curveunder impact conditions at a velocity of 30 miles per hour and withinthe range of differential pressures to which such impact bag means willbe normally subjected which substantially conform to the empiricalformula lambda 3.7p4 + 20 at differential pressures of substantially0.25 - 2.45 pounds per square inch gauge and substantially conforms tothe formula lambda 80p 40 at differential pressures above 2.5 pounds persquare inch gauge, wherein lambda is fabric permeability in terms ofcubic feet of fluid flow per square foot per minute and p is thedifferential pressure of fluid in the impact bag means in terms ofpounds per square inch gauge, the openings in said woven stretch fabricbeing continuously variable in direct relation to fluid pressures withinsaid impact bag means.